we had a pre-compliance chamber, well correlated to compliance labs.
so our inside pre-compliance testing is easy. a bit of capital to get there.
We make quick scan on about every variation to get idea of the worst.
Then the rest of our attention is on the version.
Our goal is not detectable, but running in the double KW range, we often find
some higher freq emissions.
At least a 6 dB margin, preferably more, undetectable is goal.
Once Japan called us on a violation around 5.8 GHz.
They used peak hold over time. We could not believe it, but yes peak hold
overnight in a reverb chamber found the emissions.
QP and average were near zero, except we knew what we were looking for.
Turns out the Japan authorities, or their contractors, did not know how to run
the instruments nor what the standards required. And so were a bit difficult
to deal with.
After a few months of back and forth, a comment came back that after new
testing, there is no concern.
Mexico was much easier !
Except that all their hires were fresh out of school, so it seemed.
A couple of months to coach them, and everything aligned !
ps. these are old stories, but get refreshed from the to time with new
occurrences.
On Sunday, April 7, 2024 at 03:57:50 PM EDT, David Schaefer
<[email protected]> wrote:
For EMC if the concern is emissions it would be easy to do some quick scans –
10 minutes on a peak run for each model would give you data to compare against
each other to see how much the emissions profile changes due to the
modifications. Immunity would take longer but the manufacturer should be able
to do an engineering analysis and see what might make sense/
For radios it is significantly different. Certification of a product for FCC
only applies to the product in the report and identical models as defined in
2.908. Any modifications require evaluation.
Thanks,
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From: John Woodgate [mailto:[email protected]]
Sent: Saturday, April 6, 2024 3:00 AM
To: [email protected]
Subject: Re: [PSES] I would like to hear your thoughts please
CAUTION:This email originated from outside of Element Materials Technology. DO
NOT click links or open attachments unless you recognize the sender and know
the content is safe. Please contact the TOC if you are in any doubt about this
email.
I agree: pre-scan is the way to go. Document all of the steps so that you can
produce your reasons for your decision if challenged.
On 2024-04-06 00:05, Brent DeWitt wrote:
Tough one! The problem lies in the determination of "worst case". While it
would be easy to presume that having all of the hardware populated is worst
case, it overlooks the effects of un-terminated stubs and other SI related
issues. In addition, with the world of firmware based PLL clocks and memory
traffic, it is a tough thing to determine. My opinion would be to preform the
simplest pre-scan on each configuration and base the final, rigorous
certification based on that knowledge.
Brent Dewitt
Milford, MA
On 4/5/2024 6:47 PM, Lfresearch wrote:
Hi folks,
I would like to advise a client at where to draw the line on what needs
testing. I would like to solicit opinions besides my own. Otherwise it’s the
fox urging the chicken coop…
So a manufacturer that makes a product of which there will be several variants.
All use the same board, but have different sections of circuits populated. This
may require slightly different code to run on the same uP in each case.
So.. The burning question is can we perform and analysis that postulates a
worse case hardware/software combination and test just one configuration? Or,
do we have to do every combination?
Or, are there some guidelines about where we draw the line of what to test and
what can be claimed as similarity?
Off list responses are welcome too.
Thanks,
Derek Walton
LFResearch/SSCLabs.
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OOO - Own Opinions Only
Best wishes
John Woodgate, Rayleigh, Essex UK
Keep trying
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